The present invention is directed to an improvement in locks and locking mechanisms. A flush bolt system for cylindrical lock sets is supplied by the present invention which includes anti-jimmying or anti-forcing features, and an ability to automatically lock several bolts simultaneously.
Doors are used to secure openings through exterior and interior walls, fences or other enclosures. Typically, the door is semi-permanently attached to the wall in a manner which permits the door to be moved with respect to the opening to permit passage there through, and then permit easy and fast repositioning of the door to reclose the opening. This may be accomplished by the use of hinges on one of the stiles of the door, or the door may be located on rollers, or may hang on rollers or be otherwise movable. In each instance, the hinges, or rollers, allow the door to be moved with respect to the opening, while maintaining the door in alignment to reseal the opening.
To secure the opening against undesirable or unwanted entry, the door is provided with a lock. This lock is intended to secure the door to close the opening until the lock is actuated to an unlocked status to allow the door to be moved to an open position. Such locks come in a multitude of forms, and include outside sliding latches, sliding flush mounted bolts, handled latch sets, and keyed locksets. Commonly, many such systems can be utilized in openings having multiple swinging doors to obtain proper securing of the door in the opening.
Double, or french, doors present additional problems for the door designer from the aspect of securing, or locking, the door in position. These doors are hingedly connected to a frame and meet in the middle of the frame opening. Each is commonly configured to move independently of the other, and they must be sized, and hung in the opening, with clearance therebetween for free movement in the frame but also with insufficient clearance to permit easy jimmying or prying of the doors apart. Further, to securely interlock the doors into the frame a mere bolt therebetween is insufficient. A bolt secured in one door, and extending a short distance into the other door, will not prevent motion of the doors about their hinges. To accomplish this task, an upper, and/or lower, vertical or "flush" bolt is provided which is actuatable out of the top and/or bottom of at least one of the doors and into adjacent frame members. These bolts prevent motion of the door relative to the frame when in the extended or actuated position.
The actuation of flush bolts into the door frame and floor, and accompanying actuation of the deadbolt, presents several problems to the door lock supplier. Most doors are less than three inches in width, and many modern doors are less than two inches wide. For aesthetic purposes, most lock specifiers and secondary market users require that all of the door hardware, except the handles and keyways, fit inside of, or on, the door in such a way as to minimize the exposed parts thereof. Additionally, by keeping exposed parts to a minimum, the ability of thieves or burglars to break the lock and gain entry through the door is minimized. Thus, mainly in industrial, commercial or institutional applications will exterior lock components be acceptable, and then only on the interior side of the door. Therefore, in many instances, the door lock manufacturer must supply a lock and actuation members which physically fit inside the door, leaving only handles and plates exposed. Such an installation commonly includes a lock case containing the lock actuation members, which fits into a pocket extending inward the side of the door, or a lockset, each having a pair of knobs extending from the faces of the door.
In addition to the size limitations on door hardware imposed by the size of the door, designers are faced with increasing government regulation which affects the flexibility of hardware selection common in the past. For example, in most public facilities doors must be wheelchair accessible. In that instance, when french doors are used, they must be operable by a person sitting in a wheelchair. Likewise, to increase security, doors may include mortise locks to further secure them in their frame, in the form of surface or flush mounted locks which are vertically located at the top and bottom of the door. This forecloses the use of manual flush bolts or surface bolts on the door which are disposed adjacent the top of the door, as they are out of reach of the wheel chair bound. Therefore, there exists a need for a retrofitable door lock for use in french doors, which will allow, with the turn of a single handle, the opening of both the top and bottom flush bolts.
In addition to the problems encountered with the design of accessible double door locks, the designer must include anti-theft devices to minimize the ability of thieves or others to bypass the lock and gain entry through the door.
Many doors are fitted with a rotary handle lock, commonly having retracting jaws therein which engage the rear of a bolt. These locks are installed by drilling a hole through the door adjacent the lock stile thereof, and then drilling a cross hole into the lock stile which enters the first hole. The handle lock, with the jaws, is fitted in the first hole with the jaws disposed in alignment with the cross hole, and the bolt is received through the cross hole and engaged with the jaws. Turning of the handle causes the jaws to retract into the handle lock, thus retracting the bolt into the door. As the bolt is biased to a position extending from the door, the bolt head is chamfered so that as the door closes, the chamfered portion engages a strike plate on the doorjamb, and further closing movement of the door causes the bolt to retract inward the door. Where locking is required, the inner knob will typically include a lock tab and the outer knob will include a keyed access. The outer knob is locked against movement by actuating the lock tab in the inner knob to the locked position, thereby preventing turning of the keyed handle. In this position, entry may not be gained by turning the handle to retract the bolt. However, the rotary drive commonly does not include any means of preventing retraction of the jaws which initially actuate the bolt in response to handle movement, and such devices are therefore easily forced. Thus, even where the handle is locked against rotary motion, the bolt may be forced inward the door by exerting inward pressure on the extended portion of the bolt. If further security is required a secondary, keyed, deadbolt can be installed by drilling a second set of holes in the door.
Another lock configuration is the mortise lock. These locks are disposed in a case, and the door must be mortised to receive the case. A hole drilled through the face of the door receives handles received into a mortise case. Mortise locks can include a secondary deadbolt lock therein. External knobs control movement of the latch extending outward through the door butte stile from the case.
An additional problem with lock sets which incorporate retractable non-locking jaws occurs as a result of the relatively tight alignment tolerances of the jaws and the latch bolt. Typically, a retractable, non-locking jaws type of handle set includes an inner and an outer handle, one of which may be keyed, and a cylindrical housing in which the retractable non-locking jaws are located. The latch bolt is typically housed within a cylindrical housing, and it includes an extending portion which is engaged by the jaws. When a handle is turned, the jaws housing must remain stationary, and the jaws are retracted inwardly of the jaws housing to retract the latch bolt inwardly of the end of the door.
To provide the alignment of the latch bolt and the jaws, a latch bolt bore is drilled into the end of the door, and a handle bore is drilled through the faces, i.e., through the main panel portion, of the door. If the axes of these bores intersect and are perpendicular, the jaws and the latch bolt will be in perfect alignment, and the latch bolt will move freely in response to motion of the jaws. This occurs because the jaws move linearly back and forth within the jaws housing, and they therefore provide a vector which is collinear with the axis of movement of the latch bolt to move the latch bolt in the housing. However, if the bores are substantially out of alignment, either as a result of an offset between the two axes and/or a non-perpendicular relationship between the two axes, the jaws will engage the engagement portion of the latch bolt, but the force vector provided by the jaws will not be collinear with the linear axis of motion of the latch bolt. As a result, the jaws will impose a side load on the latch bolt, which, in turn, may cause the latch bolt to bind.